Field of the Invention
The present invention relates to a method for limiting the amount of ink discharged when a photocurable inkjet printing apparatus performs printing, and a gloss determination device for verifying the gloss quality of printed matter which is produced by the photocurable inkjet printing apparatus.
Description of Background Art
Conventionally, there is known an inkjet printing apparatus that performs printing by discharging ink onto a base material (printing paper, etc.). The inkjet printing apparatus generally uses water-based ink. However, in recent years, development of a photocurable (ultraviolet-curable) inkjet printing apparatus using ultraviolet-curable ink (UV ink) has progressed. The photocurable inkjet printing apparatus performs printing by irradiating UV ink discharged onto a base material with ultraviolet light (UV light).
An inkjet printing apparatus that performs color printing generally performs printing using inks of four colors, cyan (C), magenta (M), yellow (Y), and black (K). Note that in the following the above-described four colors are referred to as “ink colors” in order to distinguish them from colors represented by combinations of the four colors. Meanwhile, when the photocurable inkjet printing apparatus uses an appropriate amount of ink, the finish of printed matter has a glossy look (high gloss). However, when the photocurable inkjet printing apparatus uses a large amount of ink at a time, ink curing failure may occur due to the characteristics of the ink, the hygroscopic properties of a base material, etc. When ink curing failure thus occurs, a surface of printed matter becomes nonuniform and accordingly the finish of the printed matter has a matte look (low gloss).
Hence, in order to obtain printed matter with a glossy look without causing ink curing failure, the maximum amount of ink (the total amount of inks of four CMYK colors that overlap each other in one pixel) is limited by a Total Area Coverage (TAC value) of an ICC profile. Note that the ICC profile refers to a document file that is set by the International Color Consortium to perform color space conversion and that defines the characteristics of a device's color space. By performing color data conversion using the ICC profile, colors can be reproduced as faithful as possible between different devices.
The above-described TAC value is set to, for example, “320%” with the maximum value of each ink color being 100%. In this case, a color that is supposed to be represented by (C value, M value, Y value, K value)=(95, 85, 95, 90) when subjected to conversion from RGB data to CMYK data is subjected to color data conversion such that the total value of the four ink colors does not exceed 320%. By thus imposing a limit on the total amount of the four color inks per pixel, ink curing failure is prevented.
Note that in relation to the present invention, U.S. Unexamined Patent Application Publication No. 2012/0281049 discloses an inkjet recording apparatus configured such that provisional curing light sources are provided separately from main curing light sources in order to obtain a desired glossy feel. In addition, Japanese Unexamined Patent Application Publication No. 2013-116605 discloses a thermal transfer printing apparatus that uses a thermal head. The printing apparatus determines an area with a predetermined density or more for each ink color as a non-glossy area, in print data.
Upon limiting the maximum amount of ink, the TAC value is set to the value of the total amount of the four color inks without taking into account the characteristics of ink, for each ink color (i.e., a value that does not take into account allocation of the four color inks). Hence, depending on the allocation of the four color inks, ink curing failure may occur. That is, there are colors that cause ink curing failure when colors that cause ink curing failure are included in a print target image, the finish of printed matter includes both a glossy-look portion and a matte-look portion, and thus, entirely uniform printed matter cannot be obtained.
In addition, in the inkjet recording apparatus disclosed in U.S. Unexamined Patent Application Publication No. 2012/0281049, the amount of irradiation light is set for each irradiation unit provided for a corresponding nozzle group, and the provisional curing light sources are controlled for each irradiation unit based on the set amounts of irradiation light. Since the configuration is such that, control according to the content of a print target image cannot be performed. In addition, since the provisional curing light sources are required separately from the main curing light sources, cost increases.
Hence, implementation of a method for obtaining printed matter with a glossy look without causing ink curing failure is sought. Further, implementation of a method for effectively obtaining such a printed matter with a glossy look is also sought.